Zeolites typically are hydrothermally formed alumina silicates of Group I and Group II elements. They can be represented by the following empirical formula: M.sub.2/n O.Al.sub.2 O.sub.3.xSiO.sub.2.yH.sub.2 O wherein "x" is generally equal to or greater than two and "M" is a cation having a valency of "n". Synthetic zeolites generally have greater uniformity and purity than do natural zeolites. Also, synthetic zeolites have a greater degree of reproduceability and, therefore, are more reliably produced for industrial applications.
Synthetic zeolites have many uses. For example, they exhibit catalytic properties which give them considerable industrial importance. Also, the crystallographic structure of synthetic zeolites makes them particularly suitable for use as molecular sieves and cation exchangers for separations.
Zeolite membranes are often formed by sequentially immersing a porous support in solutions of different reactants and then exposing the support, having the reactant solutions disposed in the pores of the support, to conditions sufficient to cause a zeolite to form, thereby forming a zeolite membrane. However, sequentially immersing a porous support into various reactant solutions causes the distribution of reactants in the pores of the support to be irregular. The quality of the resulting zeolite membrane is thereby significantly limited.
In one attempt to solve the problem of reactant uniformity, a gel of the reactants is first formed. The gel is disposed in the pores of a porous support and then exposed to conditions to form a zeolite. However, the uniformity of reactants in the gel is difficult to control. Further, gels typically do not penetrate porous supports well, thereby causing a substantial portion of the resulting zeolite to be disposed on the outside of the support rather than within the pores. Incomplete penetration of porous supports by zeolite precursors also significantly limits the performance of resulting zeolite membranes.
Therefore, a need exists for a method of forming a zeolite membrane which overcomes or minimizes the aforementioned problems.